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Basis for original (SCP) IDLH: The chosen IDLH is based on the UCC [1965] report that a 4-hour exposure to 4,000 ppm killed 3 of 30 rats, 8,000 ppm killed 10 of 30 rats, and 16,000 ppm killed 17 of 30 rats. It is also based on the statement by AIHA [1960] that some deaths occurred in rats, dogs, and guinea pigs at 4,000 ppm, but no deaths occurred at 1,000 ppm. Pozzani et al. [1959] reported that a 53,000 ppm exposure was lethal to 3 of 6 rats in 30 minutes.

Short-term exposure guidelines: None developed

ACUTE TOXICITY DATA

Lethal concentration data:

Species

Reference

LC50(ppm)

LCLo(ppm)

Time

Adjusted 0.5-hr LC (CF)

Derived Value

G. pig

Pozzani et al. 1959

5,655

-----

4 hr

11,310 ppm (2.0)

1,131 ppm

Dog

Pozzani et al. 1959

-----

16,000

4 hr

32,000 ppm (2.0)

3,200 ppm

Rabbit

Pozzani et al. 1959

2,828

-----

4 hr

5,656 ppm (2.0)

566 ppm

Rat

Pozzani et al. 1959

53,000

-----

30 min

53,000 ppm (1.0)

5,300 ppm

Rat

Pozzani et al. 1959

7,500

-----

8 hr

18,750 ppm (2.5)

1,875 ppm

Mouse

Willhite 1981

2,693

-----

1 hr

3,366 ppm (1.25)

337 ppm

Human data: Exposures to 160 ppm for 4 hours has caused flushing of the face and a feeling of constriction in the chest; exposures to 500 ppm for brief (undefined) time periods has resulted in only irritation to the nose and throat [Deichmann and Gerarde 1969].

Revised IDLH: 500 ppm

Basis for revised IDLH: The revised IDLH for acetonitrile is 500 ppm based on acute inhalation toxicity data in humans [Deichmann and Gerarde 1969]. This may be a conservative value due to the lack of relevant acute toxicity data for workers exposed to concentrations above 500 ppm.